Deaeration is an essential process operation in the liquefication and delivery of liquid photographic emulsion to a coating station. In operations where the liquefication step is isolated from the delivery, i.e. a kettle operation, the deaeration requirement of the delivery system is not severe and can generally be handled with ultrasonic equipment.
However, continuous liquefaction systems generally have very high entrained air levels which require complicated equipment such as a centrifugal vacuum degasser to ensure that coating liquids are air-free as delivered to the coating station. Examples of centrifugal degassers are shown in U.S. Pat. Nos. 2,634,907, 2,785,765 and 3,228,595. All of these centrifugal degassers can detrimentally affect the performance of the photographic emulsion. Centrifugal vacuum degassers are high energy devices which have the potential for causing sensitometric shifts in the emulsion they process. Hence, there is a need in continuous liquefication systems to deaerate the photographic material in a way which does not affect the sensitometry.
The present invention offers a unique solution to the problem outlined above. The present invention continually deaerates the gelled photographic material prior to its entering the heat exchanger. This reduces greatly the amount of entrained air within the system and allows deaeration of the liquefied photographic material by conventional means.